System of carrier-wave signaling



Feb, 23 3926.

R. V. L. HARTLEY SYSTEM OF CARRIER WAVE SIGNALING Filed 001;. 11. 1920 ln venrar:

fia/ a/r V. Lfiariley y To all whom, it may concern:

Patented Feb, 23.- 192a UNITED sT-A 'rEs 1,573,936 PATENT OFFICE,

am]: v. L. HARTLEY, or'nas'r omen; rmw'masnr, Assmnoa r wnsrxnn nnnc'rmc comm, ruconrom'mn, or imwv Yonx, n.1, a coaromrrlon or new voax.

vsa's'rim or canmnn-wayn smnnme.

Application fled Octolier 11, 1920.' Serial No. 418,058.

Be it known that LRALPH V. L Hau'rnnr, a citizenof the United States of America,

residing at East Orange, in the county of Essex, State otNew Jersey, have'invented,

certain new and useful Improvements in Systems of "Carrier-Wave Signaling,- "of i which the following is a full, clear, concise,

and exact description.

This invention relates to signaling systems 7 employmg carrierwave transmission and particularly to'such a system .wherein the.

carrier ---wave is normally impressed upon the transmisslon med um except during such time as it'may be desired to operate a signal. An object of the invention is to provide' a simple signaling'arrangement for usein combination with a telephone system where a common medium, which may in carrier currents and ordinary voice frequency currents are transmitted y means'of transmission line; Anothero ventlon isto provide a slgnahng arrangement of the type ust mentioned which will be operative-over any length of trani-imission 1 ined1um or common line used for tele honlc purposes. Stillanother object of t e m-..

vention is to., make use of theapparatus 'used for speech transmission to signaling apparatus.

A further object ofthe invention isto so arrange the apparatus of thesystem that 'each unit may functionat substantially a maximum efliciency.

These objects are attained in acarrier current telephone system wherein'afplu-i rality of carrier current transmitting an receiving stations are connected to a common transmission medium and wherein carrier waves of distinctive frequencies are normally supplied. by the transmitting stations for rece tio at cooperating receiving stations; by providing a signal at each cooperating receiving station responsive upon the withdrawal 'from the transmission medium at the transmitting station of the normally sup- Tplied oscillations. For speech transmission the normally supplied carrier wave is modulated 1n accordance'wlth voice frequenc currents. Since the carrier wave is norma ly supplied tothe transmission medium for speech transmission,- a simple method of signaling' is provided by this invention which is operative over any distances used for speech transmission and which can employ be a common ject of the in also operatefor signaling purposes, apparatus which is eflicient both for speech transmission and signaling. At the cooperatingreceiving station the modulated and unmodnlated carrier waves are translated by the detector into 'voicefrequency current for speech transmission and into unidirectional current for signaling pur ppses. According to this invention separate circuits are provided at this point, one for speech transmission and another'for signal-- mg purposes. In each of thesecircuits aglowin descriptiont ereof. will moreclearly show ow the above objects have been.-ac complished. ,It .is to be understood that other organizations of apparatus may be used to embody the-invention.

-'Referring now to the drawing line ML 1s a common transmission line for carrier telephone currents, ordinary speechcurrents, siinalmg currents and other currents for w l chit may be adapted. For 'the purpose of descrlption, three lines L L and L ter- .minating at one end in ordinary telephone stations X, Y and Z respectively are shown connected-to the common line ML, through suitable. a paratus. Stations 'X, Y and Z I may be su s cribers"stations or ordinary telephone central 'oflices. Lines L and L are adapted to transmit intelligence over the common line ML by means of high frequency carrier currents through carrier channels 1 d and 2, .while line L is adapted to em loy currents of voice frequency for telep one transmission.

Line L is asso iated with the common line ML through a filter LPF ofthe type described in Patents Nos. 1,227,113 and 1,227,114 to e. A. Gampbelhdated May 22,

1917. This filter "is of the low pass type and is adapted to suppress currents having frequencies above the" highest essential frequency of voice currents, and to transmit with substantially negligible attenuation currents of the highest essential "voice frequency and of all lower frequencies. The carrier common line ML by means of another filter HPFof the Campbell type known as a high pass filter which is adapted to pass desired currents having frequencies above the voice channels 1 and 2 are associated with the range and to suppress all those having frequencies within" the essential voice range and below. Carrier channels 1 and '2: are

substantially alike except for difierences inthe physical constants of some of'the apparatus necessitated by the use of carrier.

The carrier curren frequencies preferably 10 "employed" are those above the essential voice 'freq'uencies. Such frequencies will hereinafter be spoken of as high -trequencies ;or;

high frequency oscillations.

Av description of the apparatus' -used'in.

1 channel" 1 will now be given; The/three with the transmitting circuit T and, the

.2 receiving circuit R of channel 1.] The three Y windingcoil- HFH whichwill ihereinafter be called the high frequency hybrid coil is- 'used to connect the-transmittin circuit-T and the receiving circuit R channel. 1

' 2 with thecommo'n line ML. Associated with these three Winding coils LFI-I and HFIl are-a low .fre uency balancing network N and a high requeny' balancin network NET, respectively. 1 The networ N? bal- ,ances'the low frequency linelfi, while the network NET balances the. high frequency characteristics of the common line and the filter-HPF, and ,LPF. ,ln the transmitting circuit T there is a. modulator M -.supplied with carrier currents by the oscillator 0;. A band filter Ml of-the Cam hell type, adapted. to pass currents of t e carrier 7 frequency supp 1 received over common line ML from a coopcrating distant station (not shown)-. flhese' detected voice currents are impressed upon the low frequency line L through the voice frequency transformer 10 and the low frequency hybrid coil LFH. Band filter-DF rent which flows when no carrier waves are connected in the receiver cirbuit'R 'is of, the

Campbell type and is adapted to pass modulated and unmodulatcd carriercurrents oi the frequency transmitted by the distant cooperating station for reception by the detector D. Amplifier A is inserted between the detector l)- and the band filter DF in order to increase the intensity of the incoming currents.

nel 2 is substantiallay that an operator on line L may ed by the oscillator 1:- ()3 both unmodula-ted and modulated by? currentsof voicefrequency, is connected be tween the modulator M and the high fre'-' rier wave, Relay 6 is,

and need not be further described.

Since the apparatus associated with chandescription thereof is ne'zaeee get the attention of a cooperating operator at a distant station or may herself be signaled by thedistant operator, relays 3, 4 and in the transmitting circuit fl, and 6 and "although it ,is connected directly across the low frequency line L it does not act as a short circuit to voice frequency currents. 336133 5 is adapted to short-circuit the input of the modulatorM during the receipt of signals from thedistant operator.- Relayfi winding coilLFH whichwill hereinafter is adapted to short-circuit the; input of the be'called the lo frequency 'hybrid coil,-'is' used to conne:t., the low frequency line L L from thecarrier apparatus and to impress low frequency ringing current there- .on to signal the operator whose terminal apparatus (not ,shown) is associated with the low frequencyline L Battery 8 supplies the space current for the detector-l) and. is

connected in'series with the relay 6 and a retardation coil 9. This retardation coil 9 ofl'ers a high impedanceto currents of voice frequencyand,so prevents the shortcircuit;

ingoftransformer 10, which transformer:

efliciently passes voicecurrents from the detector I) to the low frequency hybrid coil LFH This retardation coil on the other hand furnishes a athfof relatively low resistance to the rectlfied current from detector "1) to energized the signal control relay 6,

I F'The detector I) is of the three electrode thermionicvacuum tube type, comprising a hot cathode, an anode or plate and an im-.

pedance varying. element or grid. The amount of space current which flows in such a device is dependent upon the potential oi the grid, which otential in turn is controlledby'th'e varying erefore, made marginal in its operation, that is it is not operated by the normal value ofthe space curbeiug received, but isoperated by the increased space current which flows upon the re'eipt'of carrier waves.

The signaling apparatus and relays of channel 2 are similar to those of channel 1 It is tobe understood that at the distantend of the common line ML there is located another terminalstation similar to the station shown in the drawing, comprising carrier channels coo crating with channels 1 and 2 and a low requeucy line cooperating with line L.

potential of the cari t The operation of the system is as follows: The oscillator 0 being normally connected to the-modulator M and operative, sends out a continuous train of waves of carrier frequency through the band filter MF the high frequency hybrid coil HFH,

the high pass filter HPF and-the common line ML to a cooperating distant station,'

(not shown). i Considering now for purposes of'description that channel 1 is the receivingstatiom' this train of waves is received from the common line'ML through the, high pass filte'r HPF, the'h'igh frequency hybrid coil HFI-I, the band filter DE, the-amplifier A distant operator, she will impress onzthe' line L by means of well-known apparatus (not shown) ringing current which passes over line L? through the back contacts (normally closed) of relay 7 to responsive relay 3. The-operation of relay 3 shortcircuits the output of oscillator'O byconnccting one terminal of the oscillator-to ground through the anormally' op'en front contact (now closed) of relay 3, the other terminal of the oscillator being continuously connected to ground. The train of'waves of carrier frequency-impressed upon the common line rupted'.

The operationof relay 3 also causes the I operation of. relay 5, which receives ourrentfrom battery 12 when the normally open front ontact of relay closed. The operation 0 'relay 5 disconnects the module.-

. tor M from the line L at its normally clomd back contacts and short circuits the modulator input. at its front contacts to prevent it from functioning in any way .whatever. r

i that her attention is desired.

' Thegoperhtion o f-re1ay 4 abovef'mentioned- The effect of this interruption at the distant station will now be'described in conthe battery 12,' by closing a path to ground through its back contact. 7 The operation of relay 7 vdisconnects the line L from chanme] 1 at its normally closed back contacts (now: open)- and connects low frequency signaling current source 13 to the line L through its front contacts now closed Such signaling current will operate 51 paratus' at station X to notify t e operator ML will thereby be inter -transformer such as transformer 10, is de-' disconnects the low frequency hybrid coil' LFH from the modulator at its normally closed back contacts (now open) and through'its now closed front contacts, short-. circuits the in ut. of the modulator to prevent its so-ca ed singing due to the unbalancin ofthe low frequency hybrid coil LFH w en the line I3 is disconnected at the normally closed back contacts of relay 7.

Signaling over channel 2 with its cooperating distant channel may be carried on in a similar way. Additional channels may also be employed and similarly operated.

In the foregoing it has been noted that v this invention isapplicable to long distance telephone transmission lineswhose length is limited only by the distance over which transmission by carrier currents can be accomplished; It is especially applicable when'such lines are fifty miles or more in length. of'this length is a long transmission line.

It is to be understood that aline 'It should bemoted that this invention makes use of the rectifying characteristics -of the detector's'to provide a very satisfac- "tory'method of operating a'signal control relay such as relay 6 without in any way interfering with the efiiciency of its operation as a-tr'anslating device to receive from a common line carrier currents modulated in accordance with voice frequency currents and after reception and translation to transmit the voice frequency currents to a terminal line such asL;

It is recognized in the art that if a simple signed to most efliciently transmit'currents of voice frequency, it will not be efiicient to naling currents'do not traverse'the trans- .former, which can therefore be of simple design, but still designed. to operate most efliciently'to transmit currentsof voice frequency. At thesanie time it proyides a simple signaling system by recognizing the adaptabillty and making. use of characteristics of the telephonetransmission apparatus.

in a novel manner.

Itshouldalso' be noted that this system is adapted tooperate over-any length of line used for carrier current telephone purposes. The source of'the carrier current wave for any given channel is located at the transmitting station, of that channel. The removal of the carrier waveforsignaling purposes is accomplished likewise at that station audits effective removal is therevention has been shownin the,,dravving,- it"; V

connect, slgnaling current to said line at said fore independent of the length of theicoms mon line. Y

\Vhile a particular embodiment of the in is clearly not limited to .thatparticularidisclosure. a The scope of the invention is as,

fined by the accompanying claims. What is'claimed is:

1. A carrier transmission line,an oscillai tor for normally supplying unmodulatedos- Y cillations thereto, a modulator between said oscillator and said line, means for-impress; ing speech currentsupon s'ald modulator to, modulate sa1d oscillations, a low frequencvterminal circuit, means responsive to sue l modulated oscillationsto transmit speech,

currents over said low frequencyjcircuit and means responsive to the withdrawal i said lowvfrequency' circuit.-

\ tor for normally supplying unmodulated use: cillations thereto, a modulator between said, oscillator and said line, .meansfor impressthe unmoclulate'd oscillations from said transmission l-ine to transmit a can signal over ing. speech, currents upon said modulator to modulate sald osclllatlons, means for yvlthdrawing sa1dosc1llat1ons from sa1d-l1ne,'and

' 1 means for roducing -a call signal duringthe interval. w e n the unmodulated oscillations are, withdrawn from said'line v In a' carrier wave signaling system, a transmlssion llne, an oscillator connected thereto, means responsive to low frequency 3 operation of a signal at'said cooperatingsignaling currents for sho'rtcircuiting. said oscillator, a source of low frequency signaling currents, and signaling'means controlled g i line when the detector receives speech mod:

by oscillations from said oscillator. k 4s In acarrier signaling-system, a transmission line, a plurality of; cooperating terminal stations connected thereto," a'sour'ce of high frequency oscillations atone of said stations, a relay adapted to short-circu t said oscillator uponthegreceipt of low frequency signaling currents, a source of low frequency oscillations to said line, means for modulating said oscillations at times in accordance" 11 with low-,fr'equency waves, a three eleinent signaling currents, means at a cooperating station for translatingoscillating current from saidsource"ofioscillationsl into umdirectional current, and means energized by on said line"?having its input circuit connected toj saidfline, said discharge device havingjtwo output circuits, means associated said uni-directional current to prevent the station.

5. In a,carrier signaling'fsystem,a trans-.1 mission l1ne,-"a,'plura11tyof COQPlflilllif tcr-- .ninal stations,- a modulator at one 0 said station's, an osc llatorsupplylng current to said modulator, a low' frequencydine at one;

of said stations, a relayI-pperated by signal ing current from-said hue to short-circuit said oscillator, a detector at anotherjof said stations, a signal :control relay connected the out at circuit of said detectorres )onsive Lto uni 'rectional current from said etector' and a voice frequency transformer also con: vnectedn the output circuit of said detector,

anda secondre1ay energized upon. the tie-- energ1zat1on-of-sa1d slgnal control relay; to

cooperating, station.

6; A carrier .wave system vhaving a rediiv-i 9mg channel comprising ,an electron disofcarrier current on the input circuit of w .v I

said detector.

7. In a carr1r wave signaling system, a 7 transmission line, an oscillator connected thereto, means responsive to trains of low, frequency signaling waves to with U draw. oscillations 1produced by. said oscillator from the line t roughout the duration of each of said trains, a source of low frequency -;sn'gna,-l. waves, means for impressing trams of waves from, said source upon sald 'responulated'carrier current, anda signal associated with the otherof said'circuits and operativein response to'the application andwithdrawal of carrier current on the input circuit'of said detector.

9. Atransmission line, means at onestation thereon forsupplying' high frequency electric discharge deviceat anotheristationl with one of said outputcircuits for giving an a Y indication of the presence or absenceof-high frequency oscillations on said line, and

.ineans-ass ciated with the other output'circuit for giving anmdicat on when said oscillations are modulated in accordance with low frequency waves.

i In'witnesswhereof, 'Ihereunto subscribe 1 nybname this 7th day of October, A. D, RALPH V. L, HARTLEY. 

